Method of removing the fused non-ferrous or ferrous metal stickers from slag pot ladles

ABSTRACT

A method of removing a metal sticker from a metal slag pot ladle. A step is taken of injecting cryogenic freezing gases into the ladle, while taking care to avoid contact of the freezing gases with interior walls of the ladle. A step is then taken of lowering a temperature of the metal sticker until the metal sticker shrinks and pulls away from the interior walls of the ladle.

FIELD OF THE INVENTION

The present invention relates to a method of removing the fused non-ferrous or ferrous metal stickers from slag pot ladles and associated vessels.

BACKGROUND OF THE INVENTION

In the steel making industry use is made of the slag pot ladles, these slag pot ladles are made of ferrous metal and are used to carry slag deposits from steel making furnaces.

The slag pot ladles are prepared by partially filling the slag pot ladles with slag to prevent non-ferrous or ferrous metal deposits mixed with the slag that are poured into the ladles during the operation of removing slag from the steel making furnaces, these non-ferrous or ferrous metal deposits at times become fused to the interior surface of the slag pot ladle.

In order to return the slag pot ladles back into service the fused non-ferrous or ferrous metal stickers must be removed from the interior of the slag pot ladle. At the present time the removal of the fused non-ferrous or ferrous metal sticker is performed by oxygen lancing. This oxygen lancing is conducted by using time consuming, physical manpower, consisting of numerous workers entering into the slag pot ladle and cutting the fused non-ferrous or ferrous metal sticker from the slag pot. This cutting process commonly damages the interior of the slag pot ladle, creating damage to the interior surface of slag pot ladle. This current process exposes workers to unnecessary health & safety risks due to lancing gases and hot molten metal. During the lancing process, gases, and toxic brown fumes are released into the atmosphere creating a negative environmental impact. It is difficult to predict when the slag pot ladle will be returned to service due to the varied characteristics of the fused non-ferrous or ferrous metal.

SUMMARY OF THE INVENTION

According to the present invention there is provided a method of removing a metal sticker from a metal slag pot ladle. A step is taken of injecting cryogenic freezing gases into the ladle, while taking care to avoid contact of the freezing gases with interior walls of the slag pot ladle. A step is then taken of lowering a temperature of the metal sticker until the metal sticker shrinks and pulls away from the interior walls of the slag pot ladle.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein:

FIG. 1 is a side elevation view, in section, of slag pot ladle requiring treatment in accordance with the teachings of the present method.

FIG. 2 is a side elevation view, in section, of the slag pot ladle illustrated in FIG. 1, with temperature probes attached

FIG. 3 is a side elevation view, in section, of the slag pot ladle illustrated in FIG. 2, with hose line and diffuser attached.

FIG. 4 is a side elevation view, in section, of the slag pot ladle illustrated in FIG. 3, after cryogenic treatment.

FIG. 5 is a side elevation view, in section, of the slag pot ladle illustrated in FIG. 4, with the metal stick being dumped from the slag pot ladle after cryogenic treatment.

FIG. 6 is flow diagram representation of the removal of a fused non-ferrous or ferrous metal sticker in accordance with the teachings of the present method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred method of removing fused non-ferrous or ferrous metal stickers from slag pot ladles will now be described with reference to FIG. 1 through FIG. 6.

Referring to FIG. 3, a gas diffuser 12 is placed over a metal sticker 14 stuck to slag pot ladle 16. Gas diffuser 12 is part of a cryogenic gas injection system, which includes a hose 18, which leads to a cryogenic gas source (not shown). Cryogenic freezing gases, such as liquid nitrogen, are injected into slag pot ladle 16, while taking care to avoid contact of the freezing gases with interior walls 20 of slag pot ladle 16. Referring to FIG. 4, a temperature of metal sticker 14 is lowered to below −80 degrees Celsius, until metal sticker 14 shrinks and pulls away from interior walls 20 of slag pot ladle 16. The temperature of slag pot ladle 16 is monitored by means of temperature probes 21. It will be appreciated, that the pulling away from interior walls 20 is a product of time and temperature. It may take twenty four hours at −80 degrees Celsius, and considerably less time at −196 degrees Celsius. The temperature is lowered gradually in order to avoid thermal shock to slag pot ladle 16. Referring to FIG. 5, metal sticker 14 is then taken and dumped from slag pot ladle 16.

The preferred method involves subjecting a non-ferrous or ferrous sticker from a slag pot ladle or associated vessels, having a surface which is fused to the slag pot until the fused sticker pulls away from the slag pot ladle. The Cryogenic temperature range starts at −80 degrees Celsius. It will be understood that the method works with a combination of temperature and time. As the temperature is reduced within the Cryogenic temperature range the less time it takes for the fused sticker to pull away from the interior surface. In test proving the concept, a temperature range between −80 degrees Celsius and −196 degrees Celsius was used. In order to avoid thermal shock of the slag pot ladle, the temperature of the slag pot ladle sticker must be gradually brought down into the Cryogenic range and cryogenic liquid/gas must be statically injected onto fused sticker. In tests proving the concept the slag pot ladle sticker was brought down gradually at strategic points through the injection system to avoid Cryogenic Nitrogen/gas from contacting the slag ladle interior walls. There was dwell time of approximately two to twenty-four hours depending upon the temperature used. Once the sticker is separated from the interior wall removal of the fused sticker becomes an extremely simple matter.

The present method of removing fused non-ferrous or ferrous metal from the slag pot ladle simplifies the removal, reduces the environmental impact, health risk exposure and lowers the cost of removal.

Operation in accordance with the Flow Chart set forth in FIG. 6 will now be described with reference to FIG. 1 through FIG. 5.

Sticker Removal from Melting Slag Ladle

-   1. Ensure the required liquid nitrogen (Ln2) storage tank level is     adequate for the removal process.     -   Measure the amount contained in the tank by visually reading the         gauge.     -   Work out an estimated flow rate vs. estimated time of         introduction. This will provide an estimated amount required to         complete the process.     -   Note: Keep in mind both the atmospheric temperature and the         starting slag ladle and sticker temperature. -   2. Referring to FIG. 1, conduct ajoint inspection of the intended     slag ladle 16.     -   Each slag ladle must have ajoint inspection consisting of the         client representative and either the Cryogenic operator or         supervisor.     -   Any cracks or abnormal markings must be documented.     -   Cracks must be measured in imperial measurement and documented. -   3. Once the slag ladle 16 has been delivered to the Cryogenic area,     prepare the slag ladle area for the process     -   Area must be flagged off and identified with caution tape.     -   Only workers assigned to the Cryogenic process are permitted in         the immediate area.     -   Visitors must sign in and be escorted into the area by the         Cryogenic operator to view the operation.     -   Access to area is the Cryogenic operator responsibility. -   4. Referring to FIG. 2, apply the temperature probes 21 to the slag     ladle 16, using a hand grinder.     -   Appropriate safety equipment, safety glasses in addition to a         grinding shield are required when grinding a clean surface on         the slag ladle.     -   When probes are attached to the side of the slag ladle, muffler         tape is used as the optimum fastener. Gloves must be used at         this stage. -   5. Record the starting temperatures.     -   Using the temperature measuring units, starting values must be         taken.     -   Slag ladle temperatures must be below 80 degrees Celsius before         the Cryogenic process begins. -   6. Record all history for the slag pot ladle.     -   Slag ladle history should consist of the time the slag ladle has         been out of service, sticker history, level of the sticker,         sticker composition -   7. Referring to FIG. 3, insert the diffuser 12 into the slag ladle     16.     -   Keep area clear while lifting diffuser into the slag ladle. -   8. Introduce liquid nitrogen (Ln2) through the diffuser 12.     -   Note: Lower temperatures may be found in areas of the slag         ladle.     -   Introduction of Ln2 should be slow at the beginning with liquid         being visible in 2 to 3minutes of introduction.     -   Once the liquid nitrogen (Ln2) is visible on the top of the         sticker top, liquid nitrogen (Ln2 should flow enough to maintain         a full bowl into the identified pockets on the top of the         sticker. The Ln2 should be allowed to boil off enough within the         pockets to prevent any Ln2 to roll off the sticker onto the slag         ladle but to maintain the bowl effect.     -   Note: (Ln2 must not roll onto any slag ladle surface)     -   Note: The diffuser may have to be re-positioned away from the         identified area. -   9. Monitor temperature of slag pot ladle.     -   Operator must continually monitor the temperatures of the slag         pot ladle by recording each temperature probe every half hour.     -   Operator must physically monitor the radiant temperature of the         slag pot ladle by walking around the slag pot ladle feeling for         temperature variation. (Caution must be taken when the slag pot         ladle is hot enough to burn the skin.     -   Hot areas are most typically found at the bottom of the slag pot         ladle, decreasing in temperature as you work your way to the         top.) -   10. Record “popping” or sticker “cracking” sounds.     -   Operator must record all abnormal occurrences. -   11. Slag pot ladle dumping     -   Once cryogenic process is complete arrange for slag pot ladle         dumping -   11. Escort of the slag ladle carrier.     -   The slag pot ladle will be moved to the dumping area, following         all safety procedure in place at the site -   12. Referring to FIG. 5, the dumping of the slag ladle. -   13. Record and document     -   Cryogenic operator must visualize and document the time the         sticker had been dumped and number of attempts to dump.     -   Any other pertinent notes will be taken at this time.

In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claim. 

1. A method of removing a metal sticker from a metal slag pot ladle and associated vessels, comprising the steps of: injecting cryogenic freezing gases into the slag pot ladle, while taking care to avoid contact of the freezing gases with interior walls of the ladle; and lowering a temperature of the metal sticker until the metal sticker shrinks and pulls away from the interior walls of the slag pot ladle.
 2. The method as defined in claim 1, the metal sticker temperature being lowered gradually in order to avoid thermal shock to the slag pot ladle.
 3. The method as defined in claim 1, the metal sticker being subjected to temperatures between −80 degrees Celsius and −196 degrees Celsius.
 4. The method as defined in claim 1, including a step of dumping the metal sticker from the slag pot ladle.
 5. A method of removing metal stickers from a metal slag pot ladle, comprising the steps of: placing a cryogenic gas injection system over the metal sticker; injecting cryogenic freezing gases into the ladle, while taking care to avoid contact of the freezing gases with interior walls of the slag pot ladle; lowering a temperature of the metal sticker to below −80 degrees Celsius until the metal sticker shrinks and pulls away from the interior walls of the slag pot ladle, the temperature being lowered gradually in order to avoid thermal shock to the slag pot ladle; and dumping the metal sticker from the slag pot ladle. 